It is well known to use so-called active chilled beams for air supply and simultaneously conditioning room air. By that the supply air is supplied to the chilled beam and further out of the nozzle or nozzles of the beam to the room, an induction flow of room air is created and which is drawn through the chilled beam and an integrated heat exchanger therein. The heat exchanger is liquid connected and cools or heats the air flowing through by heat exchange. Thus the passing air flow circulation is conditioned and the circulation airflow is, after the heat exchanger, mixed with the supply air in a mixing chamber, and the total air flow exiting the premises again. This will make the premises both provided with supply air and simultaneously conditioned.
Furthermore, it is well known in air treatment technology to use VAV (Variable Air Volume), i.e. let either the user control the flow of air to the premises, for example via a push button for forced air flow, or let the system regulate by indication of a presence sensor, CO2 sensor, room temperature sensor, etc., thus controlling the air flow to and from a premises—so-called demand-controlled air flow control. The main reason for this type of control is energy saving and hence reduced operating costs for the plant while it is logical to ventilate and conditioning air only when the demand exists. In several markets, including the Swedish, there are demands for specific minimum air flow for the building's sake, and in Sweden this means an air supply of at least 0.35 l/s, m2. The commercially available VAV solutions are based on that the air handling system comprises a number of damper devices in different parts of the duct system, which regulates the air flow in the respective duct in which the damper device is located. It is also common that these damper devices are provided with an orifice plate for measuring the pressure drop over the flange, thereby enabling calculation of the actual air flow. Usually the plant is divided into sections with such branch dampers for controlling air flow to each branch duct. If one want VAV regulation down to the individual room level, the prior art states that each channel to each room must be provided with such a VAV damper device to ensure that the air flow to the room will be the correct. If one does not use control right down to the room level but collective control, the airflow to a unique room cannot with certainty be controlled/regulated if the air flow demand of the group varies. For example, if the supply air flow demand to some of the meeting rooms in an office space decreases, and these are located in the same group/branch duct, the system will down-regulate the air flow to the group and then also the pressure drop in the air duct is reduced. If then for example one of the meeting rooms is still in use and thus should have normal air flow, it is not certain that this will be the correct/projected air flow because the pressure is not the same as at full load in that group. Thus, it is not certain that the comfort level in the room will be kept. The system is then, at least at room level, pressure-dependent, since a certain pressure is needed before the chilled beam in order to know that it delivers the right amount of air and thereby is able to control the room climate. In order to gain control of the respective rooms thus usually an individual control for each room is installed. The disadvantage of providing the system with individual VAV dampers is that the system gets a built-in and energy consuming pressure drop at each VAV damper. The pressure drop across the orifice must exist and must also not be too low to obtain accuracy in the measurement and control of which current air flow that is present in the duct. In a system with chilled beams coupled to this type of VAV solution is, so to speak, the chilled beam pressure dependent in order to genuinely know that the actual and projected air flow delivered to the room, which is a prerequisite for having control of delivered and desired air volume and delivered cooling effect, as it is dependent of the supply air flow and the induction by the chilled beam at a certain static pressure of the same.
The alternative to reduce the pressure dependence and pressure variation is that for example, build a so-called ring system, which in its ideal form can be exemplified by an office floor where the main supply duct, for example of the supply air, is up-sized and connected to a continuous ring for the entire floor. The duct is dimensioned to always having a low and stable air velocity in the main duct and in that the duct cross section is large, and that each duct branch to each room in principle proceeds directly from the ring duct, the available pressure at each branch in principle gets equal despite some variations in airflow, whereby the air flow for a given demand can be largely met at room level. However, also this solution is based on that the actual air flow delivered out of a single chilled beam or the like is dependent on that the pressure is known and constant. Furthermore, the actual delivered quantity of air still is unknown because no actual registration/measurement is made in the final product/chilled beam. These oversized air ducts require much space, which for example influences the number of floors that can accommodate in a taller building, and also affects other installations that are to share in the installation spaces in the ceiling and vertical shafts. Similarly, a duct system which is not constructed as a ring still have similar characteristics as described above, by that duct dimensions are chosen sufficiently big to get low speed in the ducts, and thereby reduce the pressure dependence in the same manner as in the ring system.